This invention relates to liquid ring compressors in general and more particularly to an improved arrangement for insuring sufficient liquid during start up in a compressor having a liquid separator.
Liquid ring compressors are well known in which a ring of liquid co-rotates with an impeller eccentrically disposed within a housing to obtain the necessary pumping action to compress the gas. In such compressors, it is well known to provide liquid take-off points which are acted upon by the ring of liquid to supply liquid to auxiliary liquid circuits through external connecting lines. These auxiliary liquid circuits are used to seal gaps between the impeller and housing, to lubricate shaft seals if necessary and to replace the portion of the operating liquid which is carried off with the compressed gas and is not separated out. This operating liquid maintains the required liquid ring within the housing and cools the housing. This is necessary since the liquid ring absorbs the major portion of the compressor power and is heated up in the process.
In liquid ring compressors which operate using expensive or environmental polluting operating liquids, an operating liquid circuit is generally provided in which the liquid which is expelled along with the pumped gas is completely returned to the compressor through the use of a heat exchanger. In other words a liquid separator is provided at the discharge of the compressor to separate the liquid in the gas and return it to the compressor.
Normally this return is accomplished by means of the compressor suction. In such a system, after the compressor is stopped only a portion of operating liquid remains in the housing, which portion is sufficient, upon restarting, to form a thin but operative liquid ring. However, due to the fact that a portion of the operating liquid is carried away with the gas being compressed, this thin liquid ring can be further thinned within a short period of time to the point where the liquid ring is no longer in engagement with the impeller resulting in a sudden cessation of the output. This results directly from the fact that during start up the suction is not sufficient to draw back into the compressor the separated liquid from the liquid separator. To overcome this problem it has been typical in the prior art to provide separately driven circulating pumps e.g. centrifugal pumps, in the circuit between the liquid separator and the compressor. However, such pumps require maintenance, are expensive and take up space.
In view of this, it is the object of the present invention to provide, in a simple fashion, without the need for separately driven pumps with moving parts, perfect starting and continuous operation of the type of compressor described above.